You have it pretty close. They started the use of remote trucks with sensors a few years ago when some scientists proved that readings taken by using laser beams and other types of sensors on passing vehicles were just as effective as having to take it to a testing center and pay the $25 fee.

They are located on heavily traveled feeder roads into Denver, not just the interstate, and they are on the uphill ramps. You get a notice on your next vehicle registration form that you have either failed or passed the remote reading. If you fail, you have to go for the anal probe testing.

If you buy a used vehicle, you have to take it to a testing center before you can register the vehicle.

From what I can gather, diesel engine vehicles in Colorado are not tested by the regular system. Instead, there are private garages that do the testing and repair. Judging from the number of big pickup trucks running around belching clouds of black smoke, this might be the time for the state to take a look at what's going on with some of those mechanics.

Buy as much VW stock as you can now. The Germans have always been too smart for their britches, I can say that as I have German heritage. They make an incredible product, when this is over they still will.
John

Buy as much VW stock as you can now. The Germans have always been too smart for their britches, I can say that as I have German heritage. They make an incredible product, when this is over they still will.
John

Actually all vehicles that originally had to meet any Federal Emissions stands are still "Subject" to emissions inspection, regardless of age. States can make their on decisions as to inspect or not.

Here in CA, where we respect air quality, air cooled Beetles, with modified engines, can and do get tagged for emissions violations. For that reason the "No engine cover" look has all but disappeared to hide the dual carbs etc. that were added.

And states can change inspection cut-off dates. Years ago, when I lived in VA, they started requiring emissions inspections on cars hat had been previously exempted. Lots of surprises for the Good Ol Boys......

And last.... smog cams have already been challenged in court, and won.

Calculated indices have determined that air traffic does not significantly contribute to the global budget of NOx, but the VW diesel does.Now we know the real reason it is referred to as Laughing gas!

I could not guess how many defective EGR valves I have found due to a design which promotes the formation of carbon deposits.
Every one of these results in more NOx emissions at ground level.
This violation appears to be a simple program variance to the EGR program.

It appears that the complaint against VW has to do with NOx emissions and not to black smoke.
As usual the media have reported this with headlines which read like this...
"Volkswagen cheats... intentionally multiplies pollution 40 times".